There are basically two prior art schemes which have been used to detect the last dialed digit of a dialed telephone number. These two prior art schemes are generically described as a fixed time delay and the North American Dialing Plan (NADP) scheme.
The most common and simplest scheme, the fixed time delay scheme, is implemented by receiving DTMF digits and simply waiting a preset amount of time after the last digit before extending the call to the called site. This set amount of time is typically five seconds, i.e., if a digit is not received within five seconds of the last dialed digit, then the system assumes that the last digit has been dialed. The drawback of such a scheme is evident; the delay period is longer in duration than even the time required to dial an eleven digit computer generated phone number.
The second prior art scheme takes advantage of the NADP. The first digit entered is examined, and if it is a "1", then ten digits are to follow. If the first digit is not a "0" or "1", then the next two digits are checked for "11", i.e., "411", "711" or "911." If this test also fails, then the system assumes a seven digit number will be dialed. As soon as seven digits are entered, this phase of dialing is determined to be complete. While the NADP scheme is certainly much faster than the fixed time delay scheme, it is not universally applicable, e.g., it will not work with some of the newer numbering arrangements such as "10288."
Accordingly, it is a primary object of the present invention to provide a new and improved system and method for efficiently recognizing the last digit of a standard dual tone, multiple frequency telephone number.
It is another object of the present invention to provide a new and improved system and method of efficiently recognizing the last digit of a telephone number dialed from a standard DTMF telephone which greatly reduces the time needed for the dialed number to be transmitted from a local unit to a remote unit.